The Redpath Library was bestowed upon McGill in 1893 due to the beneficence of Peter Redpath, owner of Redpath Sugar and one of Montreal's leading citizens at that time, and his wife Grace Wood. The couple also donated the Redpath Museum, located just northeast of the library. This was a very timely gift since, prior to this building, all the University's acquisitions had resided in Molson Hall, the west wing of the Arts Building. The University had begun to rapidly expand in the 1890's and all the rooms in Arts were needed as lecture spaces. The first librarian of Redpath was Charles H. Gould who initiated the Library School and the Traveling Libraries Program which lent books to towns not fortunate enough to have their own library. He was one of the most prominent and pioneering librarians in North America and from 1908 to 1909 was made president of the American Library Association.

The architect of this Richardsonian Romanesque building was Sir Andrew Taylor, born in 1825, who hailed from Edinburgh and had been educated at the Royal Academy in London. His wife was related to Sir William Dawson, the current principal, and he himself was a member of the Redpath family. Redpath Library was one of six edifices commissioned from Taylor for the McGill campus. In designing this structure, Taylor put its function, layout, and special needs ahead of its proportion and ornamentation. The building was considered one of the most innovative of its time. Taking into account the purpose of the building, he proposed that the stacks be defined by a steel frame and grids with thick glass floors to allow the light to pass through all three floors while making the whole fire proof, an amazing feat for 1893. A fire proof door separated the stacks from the main library and reading room which had floors of terra cotta and a roof of slate and copper. The only wood used was in the massive, oak beams that supported the upper floors and were capped at either end by fearsome dragon heads both inside and outside the building.

Although the stacks were very thoroughly designed, the reading room was not as well thought out. The high stone walls echoed even the smallest whisper, making it necessary to forbid conversation of any sort, although there was apparently a considerable amount of traffic in note passing. The extensive use of stained glass windows kept out much of the natural light. The chandeliers hung from the high ceiling and the reading lamps could not compensate enough for the lack of light. The entrance to the building was grandiose, yet it opened onto the reading room which caused further disturbance to the students within. Taylor was criticized, even in his time, for creating an unused tower over the front entrance of the building, yet it gave the building a look of dignity and importance appropriate to a university campus.

There is a considerable amount of ornament about the Redpath Library, even though Taylor's primary concern was with its function. Mrs. Grace Redpath donated a large amount of stained glass which she commissioned from Clayton and Bell in London, England. Poetry, the Fine Arts, and Music are the subject of the three large lancets in the east. Homer and Virgil are among the poets depicted, the writers include Shakespeare and Molliere, artists from Zeuxis to Michelangelo and Rubens to Wren are shown, and Bach, Beethoven, and Wagner stand with many other composers. The five lancets in the west above the balcony represent Law, History, Philosophy, Astronomy, and Medicine. Several wood and stone carvings exist on the timbers and exterior walls. Strange creatures and gargoyles adorn the roof at the ends of the beams. Two in the interior are portraits of Peter Redpath and Sir Andrew Taylor themselves. The outer walls, built of Montreal limestone in fitting with the rest of the campus, have the symbols of the Four Evangelists carved onto them to remind students of the highest possible wisdom. On the south facade are the crests of two major publishing companies, one represented by a swan, the other by a dolphin. Over the door is the Redpath crest, an ostrich holding a key.

Between 1900 and 1901, Taylor extended the already full stacks at the request of Mrs. Grace Redpath. In 1921 the library was again expanded, this time by Percy Nobbs and George Taylor Hyde. Their expansion fit in very well with Taylor's style, unlike the later expansions which provide much more space, but do not even attempt to continue Taylor's idea. From 1952 to 1954 the firm of McDougall, Fleming and Smith extended the library to the south creating several large new reading areas with glass walls on the main floor, and room on other floors for several special libraries, such as the Blacker-Wood Library of Zoology and Ornithology (now the Blacker-Wood Library of Biology) and the Blackader-Lauterman Library of Architecture and Art. When McLennan Library was erected just south of Redpath in 1969, the main floor of the 1952 addition to the library was extended to create a walkway between the two buildings. In constructing the 1952 expansion to Redpath, the east wall of the Nobbs and Hyde 1921 projection was entirely enclosed and the use of Taylor's reading room as part of the library came to an end. At this time, the floor of the Taylor's elegant room was redone in wood, the tables were cleared away, and the reading room was reopened as Redpath Hall, an auditorium for the University used today mainly for music recitals and receptions. In 1981, a replica of a French Renaissance organ was donated to the hall to emphasize its new musical role and can still be heard regularly during the year.